Dart Requires Chilkat v11.7.0+

Encrypt a PDF for a Certificate Instead of a Password

See more PDF Protection Examples

Demonstrates certificate security, where a PDF is encrypted for one or more recipients and each opens it with their own certificate and private key. No password is involved. Only the public certificate of a recipient is needed to encrypt. Each recipient has its own permissions, and the changeSecurity permission gives a recipient owner rights. PreLoadCheck tells an application that a file is certificate-encrypted and which certificates can open it. A PDF that cannot be opened, because no matching certificate and private key were provided, fails to load. Dart

import 'package:chilkat/chilkat.dart';

void main() {
  // This example requires the Chilkat API to have been previously unlocked.
  // See Global Unlock Sample for sample code.

  // The PDF used in this example is available at two_page_memo.pdf

  // The recipient's certificate.  Only the public certificate is needed to encrypt.
  final recipient = CkCert();
  try {
    recipient.loadFromFile('qa_data/certs/recipient.cer');
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  final pdf = CkPdf();
  try {
    pdf.loadFile('qa_data/pdf/two_page_memo.pdf');
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  // Call AddEncryptCert once for each recipient.
  try {
    pdf.addEncryptCert(recipient);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  // recipientPermissions[0] belongs to the first certificate added.  changeSecurity gives that
  // recipient owner rights, so the file can be managed later.
  final json = CkJsonObject();
  json.updateString('method', 'certificate');
  json.updateBool('recipientPermissions[0].changeSecurity', true);

  final jsonOut = CkJsonObject();
  try {
    pdf.protection('encrypt', json, jsonOut);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  print('method: ${jsonOut.stringOf('pending.method')}');
  print('algorithm: ${jsonOut.stringOf('pending.algorithm')}');
  print('recipients: ${jsonOut.sizeOfArray('pending.recipients')}');

  try {
    pdf.writeFile('qa_output/memo_for_recipient.pdf');
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  // PreLoadCheck says how the file is protected, without loading it.
  final reader = CkPdf();
  final info = CkJsonObject();
  try {
    reader.preLoadCheck('qa_output/memo_for_recipient.pdf', info);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  print('saved file, method: ${info.stringOf('method')}');
  print('saved file, recipients: ${info.sizeOfArray('recipients')}');

  // The recipient opens it with the certificate and its private key, here from a .pfx file.
  // (On Windows, a certificate that is installed in the Windows certificate store with its private
  // key is found automatically when the PDF is loaded, and SetDecryptCert is not needed for it.)
  final myCert = CkCert();
  try {
    myCert.loadPfxFile('qa_data/pfx/recipient.pfx', 'pfx-password');
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  try {
    reader.setDecryptCert(myCert);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  try {
    reader.loadFile('qa_output/memo_for_recipient.pdf');
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  final empty = CkJsonObject();
  final loadedInfo = CkJsonObject();
  try {
    reader.protection('getInfo', empty, loadedInfo);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  print('opened with: ${loadedInfo.stringOf('loaded.openedWith')}');
  print('pages: ${reader.numPages}');

  // Sample output:

  // method: certificate
  // algorithm: aes-256
  // recipients: 1
  // saved file, method: certificate
  // saved file, recipients: 1
  // opened with: certificate
  // pages: 2
}